Thank you for this picture. If the gears inside are the originals from this case, then WOW you have an early non-Total-Spline set, sometime from 1996 to 1998. I even checked our
Official Crawler # Registry, the 4th oldest post on this forum, but this serial number is not in the list. Bummer!
So now we have a serious problem. The gears that you have were made by Advance Adapter's old gear cutter (who has since passed away). They were made on old equipment and are a poor design because 1) they used a pressed together multi-piece shift hub design that were prone to falling apart, and 2) these hubs lacked a 2-degree taper to prevent the shift collar from wandering or "popping" out of gear. You can read more about the gear popping out issue
here (reply #3). It is because of these old gears that the Heavy Duty Shift Springs came into existence (as a band-aid to remedy a bad shift hub design). You can learn more about our HD shift springs
here which I strongly recommend for safety sake if you are to use these gears -- hopefully the case already has a driver's side HD shift spring installed. Since we did away with this old shift hub design on our 4.70 gears I believe in the fall of 1998, Heavy Duty Shift springs are but a novelty item.
The serious & bad news for you is that because these are our old gears based on an obsolete design, having been since redesigned by Marlin with vastly improved features and produced by Toyota's own gear cutter in Japan, they are not compatible with our modern day gear sets. You could purchase a new Total-Spline 21-spline 4.70:1 input from us and try it out ... but there is no guarantee as to how long your old idler gear will hold up... It's not something I would recommend doing. The only thing I'd recommend is to come up with a pre-1999 21-spline 4.70 input gear. I'll take a look in our trophy room tomorrow to see if we have any used two-piece inputs laying around that are in useable condition, but this is a very long shot bet.
To rephrase the original question - can I move the new gear from the 23 spline shaft to the 21 spline shaft to keep the gear ratio correct? Is this possible or are the gear and shaft all one solid machined piece?
Sorry but the input shaft is part of the input gear and the two are inseparable.
Here is an example picture of an "input gear", which contains the input (where the splines engage with a coupler) and the gear that meshes with the low range counter shaft. This picture is our Turbo Total-Spline 23-spline input (
link) which you'll notice right away looks different than the input you have:
The input splines are indeed connected to the input gear.
As mentioned, I will take a look tomorrow to see if we happen to have a good used pre-1999 21-spline input laying around, but I really don't give this much of a chance. Short of this, here are your basic options:
1. Purchase a new, improved 21-spline MC gear set, sell the one you have to someone who needs a 23-spline set.
2. Purchase a 23-spline dual case adapter and build a dual case setup where you'd have your current transmission with it's 21-spline output coupler -> 21-spline Crawl Box input -> 23-spline Crawl Box Coupler ->
23-spline 4.70 Input, done! This is the method ryantowry_81 mentioned above, and is what I did with my own truck: I have a 21-spline output transmission but have converted my drive train downstream of my first Crawl Box to all 23-spline parts for maximum strength (see
reply #807 here for more info).
3. Swap in a Turbo transmission (very hard to find and are very expensive), or a W59 Tacoma 5speed, or a V6 transmission, where the later two options would require also purchasing a Transmission-to-Transfer Case Adapter Kit (
see here) which use a 23-spline conversion coupler designed for our 23-spline 4.70:1 input gears.
I wish I had better news for you Sir. I know you mentioned about dual cases being out of the budget for now... This might be a project you'll have to put on hold until you can come up with some extra fundage $ to make the 23-spline gear kit compatible with your truck. Of the negatives mentioned above regarding our old & original 4.70 design, I'd like to point out that the set you have is still around so you've obviously got a good set on your hands! It's a testimony to our products and would be really cool if you could put it to use! I happen to have MC08-R10 serial number #001 in my truck -- the World's very first Billet Aluminum Rotated Dual Case Adapter -- and I am extremely proud of my long lasting Marlin Crawler parts!
Regards,
BigMike
